Counterion condensation on polyelectrolyte chains adsorbed on charged surfaces

C. F. NARAMBUENA; E.P.M. LEIVA; E. PÉREZ

COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2015 vol. 487 p. 49 - 57

0927-7757

We developed a Monte Carlo systematic study into the effect of counterion condensation on the polyelec-trolyte adsorption process on charged surfaces. Polyelectrolyte is modeled as a full-flexible chain whosesize is characterized by the equilibrium bond length and the number of monomers per chain. The smallanions and cations are explicitly modeled.The adsorption proceeds with a non-trivial counterion condensation degree on the polyelectrolytechain. When the polyelectrolyte coverage degree on the surface is low, the chain looses most of itscounterions (anions), due to their electrostatic repulsion with the negatively charged surface. This effectis more evident when the equilibrium bond length is shorter. Counterions are recondensed as coveragedegree increases, and this is attributed to two main energetic reasons: first, the chains adsorbed causeshielding of anion-surface repulsive electrostatic interaction; second, the repulsive interaction betweenchains adsorbed on the surface is shielded by the condensed counterions on these chains.The amount of polyelectrolyte adsorbed and degree of condensation counterions reaches a plateau asa function of the number of chains added to the simulation box. At this point surface charge is overcom-pensated in a similar magnitude for the different chain types. However, the adsorbed chains keep mostof their condensed counterions when the equilibrium bond length is shorter.